
In order to solve (REF ) we review the method proposed in [1]}, [2]} known as master equation formalism. If we consider \( G(\phi )\equiv A^{\prime }(\phi )\)  the solution of the equations of motion can be expressed as
\(A(\phi )&=A_H+\int _{\phi _H}^\phi d\tilde{\phi }G(\tilde{\phi }),\\B(\phi )&=B_H+\ln \left(\frac{G(\phi )}{G(\phi _H)}\right)+\int _{\phi _H}^\phi \frac{d\tilde{\phi }}{6G(\tilde{\phi })},\\h(\phi )&=h_H+h_1\int _{\phi _H}^\phi d\tilde{\phi }e^{-4A(\tilde{\phi })+B(\tilde{\phi })},\) 
